Spark plug construction



, Much 6, 1951 H. R. miel-nensrm run consmuc'non origina; lmm1 on* x, 4sama-sm# s",

F2912 Fay/3 Harold R. F'ez'c/z ier* @61W 2gb/ggf Attornegs d 4shuts-Shoot 4 Attorneqs H. n. FelcHTr-:n

sms rwc consuwcnon originar-rim on. .1i-1947 Harald R. Reich ver @M1f/eff March 6, 1951 Patented Mar. 6, 1951 UNITED STATES PATENT OFFICESPARK PLUG CONSTRUCTION Harold It. Felchter, Canton, Ohio, assignor toUnited States Quarry Tile Company, Canton, Ohio, a corporation ofDelaware (Cl. 12S-169) 4 claims. 1

The invention relates to spark plug construction and to spark plugs foruse in internal combustion engines for automobiles, aircraft, orwherever it is desired to ignite a combustible mixture, and thisapplication is a division of my application, Serial No. 777,350, filedOctober l, 1947, now U. S. Patent 2,478,259, granted August 9, 1949.

In a usual spark plug there are included a multiplicity of parts some ofwhich are metal and which require a relatively large number ofmanufacturing operations for the production of the separate parts andtheir assembly.

In a usual spark plug there is included a metal ground shell in which atubular insulator is inserted, and the tubular insulator has a boreextending entirely through the insulator, and a rod electrode is locatedin and extends through the bore of the insulator.

At the lower end oi' the metal ground shell there is welded or otherwisesecured a ground electrode, and the lower end of the central rodelectrode is spaced from the ground electrode. It is necessary toprovide a gas sealing cement between the rod electrode and the bore ofthe insulator and it is also necessary to provide a gas tight sealbetween the insulator and the shell.

In other words a usual spark plug includes a multiplicity of parts whichmake the cost of production relatively expensive, the assembly of theparts being complicated and ditllcult to control to provide for auniform nished Product which does not deteriorate in use.

The objects of the .present invention include the provision of animproved spark plug construction which is inherently adapted for a longperiod of use and which requires less metal than a usual spark plugconstruction, metal having become scarce as compared with ceramicmaterial, and in which there is a reduction in the number of partsrequired to produce the lmproved spark plug on the one hand, and whichprovides the spark plug with substantially improved properties ascompared with present spark plugs on the other hand. One of the moreimportant of these improved properties is the minimizing of thenecessity of replacing the spark plug at intervals as frequently as hasbeen necessary lprior to the present improvements.

The properties oi the improved spark plugs of the present inventioninclude freedom from gas leakage, freedom from rapid deterioration ofthe electrodes of the spark plug, convenient replaceability of theground electrode, an arrangement of the reduced number of partspermitting broad scope in the design as to the size and shape of theparts of the spark plug, a relative arrangement of the size and shape ofthe parts of the spark plug whereby there may be a greatly increasedlength of the electrical leakage path between the central electrode ofthe plug and ground, without increasing the overall length of the plugas compared with conventional practice. A further property of one formof the improved spark plug of the present invention in addition to theforegoing is the maintaining of a constant position of the lower end ofthe central electrode. and the transfer of heat by convection throughcirculation of a conducting liquid as well as by its own conduction,from the tip of the insulator or electrode to other portions andsurfaces of the insulator.

The foregoing and other objects are attained by the spark plugconstruction, parts, combinations, and sub-combinations, which comprisethe present invention, the nature of which is set forth in the followinggeneral statement, and preferred embodiments of which together withtheir mode of use are set forth by way of example in the followingdescription, and which are particularly and distinctly Ipointed out andset forth in the appended claims forming part hereof.

The nature of one preferred embodiment of the improved spark plug of the'present invention may be stated in general terms as including aninsulator body preferably of vfired ceramic material, the insulator bodyhaving formed therein a well with an open upper end and the insulatorbody including a bottom wall extending across the lower end of the well.Electrode material is located in the well, and the insulator bodyincludes a lower end having formed thereon external threads adapted forbeing screwed into an internally threaded opening in the wall of acombustion chamber such as the combustion chamber of an internalcombustion engine. A replaceable metal ground electrode is provided onthe lower end of the insulator body adjacent the bottom wall of thewell.

By way of example, a number of embodiments of the improved spark plugconstruction of the present invention are illustrated in theaccompanying drawings forming part hereof, in which Figure 1 isa'longitudinal axial sectional View of a first preferred embodiment ofimproved spark plug hereof Fig. la is a similar view of the insulatorbody shown in Fig. l, before assembly in the complete spark plug;

Fig. 2 is a similar view of a second embodiment of the improved sparkplug construction hereof;

Fig. 3 is a similar view of a third embodiment of the improved sparkplug construction hereof Fig. 4 is a similar view of a fourth embodimentof the improved spark plug construction hereof;

Fig. 5 is a similar view of a fifth embodiment of the improved sparkplug construction hereof;

Figs. 6, 7, and 8 are views similar to Fig. la, showing modified formsof 'insulator bodies for the improved spark plugs hereof;

showing a modified form of ground electrode;

Fig. l is a view similar to Fig. 1 of a sixth em bodiment of theimproved spark plug construction hereof;

Fig. 11 is a view similar to Fig. 1 of a seventh embodiment of theimproved spark plug construction hereof.

Fig. 12 is a bottom plan view of the spark plug construction of Fig.looking in the direction of the arrows I2-I2, Fig. 10;

Fig. 13 is a transverse cross section of the spark plug construction ofFig. 10 as on the line I3-II, Fig. 10;

Fig. 14 is a view similar to Fig. 1 of an eighth 'embodiment of theimproved spark plug construction hereof;

Fig, 15 is a similar view of a ninth embodiment of the improved sparkplug construction hereof; and

Fig. 16 is a similar view of a tenth embodiment of the improved sparkplug construction hereof.

Similar numerals refer to similar parts throughout the several views.

The rst preferred embodiment of the improved spark plug hereof isillustrated in Fig. 1 and is indicated generally by I0 and includes aninsulator body II preferably made of fired ceramic material preferablyhaving a high alumina content of upwards of 92 per cent, and also otheringredients, such as set forth in any of my U. S. Letters Patents No.2,413,441, No. 2,414,367, No. 2,414,368, and No. 2,414,369.

The insulator body II is shown in Fig. 1a before assembly in thecomplete spark plug I0, and the insulator body II has formed therein awell I2 with an open upper end I3, and the insulator body II furthermoreincludes a bottom wall Il extending across the lower end of the well I2.The insulator body II is elongated, and the well I2 extendslongitudinally coaxially with the longitudinal axis I5 of the insulatorbody II. Metal electrode material is located in the well I2 which may beas shown in Fig. 1 a rod I6 of metal such as steel. The upper end I1 ofthe well I2 may be enlarged and provided with internal threads, and themetal electrode rod I6 may have an enlarged head IB which is externallythreaded and screwed in the internally threaded enlarged upper end I1 ofthe well I2. The bottom wall Il is preferably thinner than thesurrounding walls of the insulator body, and in itself seals the lowerend of the well I2, and covers the lower end of the electrode rod I6therein. The bottom wall Il preferably has a thickness between thelimits of 5 thousandths and 125 thousandths of an inch. In addition,when desirable, the electrode rod I6 may be sealed in the well I2 in ausual manner as by ceramic cement.

The insulator body I'I has a reduced lower end indicated generally by I!which includes an intermediate externally threaded portion 20 and astill smaller externally threaded extremity 2|.

The spark plug I0 furthermore includes a replaceable ground electrodeindicated generally by 22 which is made of metal such as steel or otherhard metallic substance, and which includes an internally and externallythreaded ferrule portion 23 whose internal threads are screwed on theexternally threaded extremity 2l of the insulator body II, and theexternal threads of the ferrule 23 match the externally threaded portion20 of the insulator body Il. The replaceable ground electrode 22furthermore includes one or more electrode tips or points 24 made ofnickel or like material and extending in- 4 wardly from the ferruleportion 22. The insulator body II furthermore includes a larger upperportion 2l and an annular shoulder 2l between the inner end of thethreaded portion 2l and the larger upper portions 2l, which has a largertransverse cross section than the transverse cross section at any placeof the reduced lower end II.

A metal combustion chamber wall 21 which may be a wall of a combustionchamber o! an internal combustion engine has formed therein aninternally threaded opening 2l in which are screwed the externallythreaded lower end portion 20 of the insulator body II and theexternally threaded ferrule portion 23 of the replaceable groundelectrode 22.

In using the spark plug Il the central rod electrode I6 and thegrounding metal combustion chamber wall 21 are connected in a usualignition circuit which applies a potential to the central electrode rodIt, and from the lower end thereof contacting the well bottom wall Ilpotential is applied to the bottom wall Il until its charge issufficient to cause a spark between the bottom wall I4 and the electrodetips 24.

In the improved spark plug Il the upper portion 25 of the insulator bodyII may have any desired form and dimensions which are not subject to theform and dimensional limitations of a usual spark plug where the groundshell must be crimped over or otherwise fastened to an enlargement onthe usual insulator body.

In the improved spark plug III there is freedom from gas leakage byreason of the location of the central electrode IB in the well I2, thesolid bottom wall Il of insulating material extending across the lowerend of the well I2. Thus protecting the central electrode It preventsrapid deterioration of the lower end of the electrode IB. When theelectrode tips of the ground electrode 22 become burnt oi! too much, areplacement ground electrode 22 may be conveniently and easily appliedto the insulator body I I. It is also to be noted that the length of theupper portion 25 of the insulator body II is substantial whereby thereis a greatly increased length of the electrical leakage path between theupper head I8 of the central electrode Il and the grounding combustionchamber wall 21, thisincreased length of the electrical leakage pathbeing eifected without increasing the overall length of the plug ascompared with conventional practice in spark plug construction whereground shells are used which extend a considerable distance above thecombustion chamber wall in which the spark plug is mounted.

In Fig. 2 there is shown a second embodiment of the improved spark plughereof indicated generally by IIII and which is generally similar to thespark plug Il, but in the spark plug IIB the insulator body III has abore II2 extending entirely through the body, and a center electrode IISlocated in the bore II2 has its lower end protruding below the lower endof the insulator body IIL In the spark plug IIB there is also areplaceable ground electrode |22. The spark plug Ill has all theadvantages of the spark plug III with the exception of lacking a centralelectrode in a well.

In Fig. 3 there is shown a generally conventional spark plug indicatedgenerally by 2Il including a ground shell 23| at the lower end of whichthere is screw connected a replaceable ground electrode 222 whichconstitutes one of the improvements of the present invention. The

v ground shell 230 has mounted therein in a usual manner an insulator2II in the central bore 2I2 of which there is sealed a central electrode2li in the usual manner.

In Fig. 4 there is shown aspark plug indicated generally by IIII whichis of generally conventional construction including a ground shell 330mounting an insulator body SII which is modified from conventionalconstruction by including awell SI2 having a bottom wall 3I4 extendingacross the lower end of the well SI2, this being one of the improvementsof the present invention. There is located .in the well H2 a centralelec. trode IIC.

In Fig. 5 there is shown a spark plug indicated generally by 4I4 whichis of modified conventional construction and includes a ground shell430'. One of the improved removable ground electrodes of the present linvention indicated generally by 4221s screw connected to the lower endof Vthe ground shell, and the ground shell mounts an insulator body 4IIwhich is formed to include another of ythe improvements of the presentinvention; namely a central well 4I2 havingr a bottom wall 4I4 extendingacross its lower end. A -central electrode 4I6 yis located in the well4VI2.` f l l' In Fig. 6 there is shown a modified insulator bodyindicated generally Vby 5II whichv isygen` erally similar to theinsulator body II`, the insulator body EII having formed thereinacentral well SI2 having an open upper end 5|.3 andaA bottom wall 514extending lacrossthe lower end of the well SI2. Differing from the solidbottom Wall I4 ofthe insulator'body II, the bottom wall 5I4 has amicroscopic hole 5I4jrl formed therethrough by being puncturedy by ahigh tension electrical discharge passed therethrough by plac-` ing'th'ewall 5I4 between electrodes ofv an electric circuit-in which there is a,sufcient potential dierence between the electrodes'to eiect thepuncturing. In Fig. 6, -the 'microscopic hole 5I4-I'is necessarilymagnified. i l

For properly locating the hole 5I4-I, the top face of the bottom wall5I4 slopes to a central point-` 5I4-2 which insures that thespuncturingVhigh tension electrical discharge will pass through the wall lI5I4 atthe central point 5I4-'2, the wall 5 I 4 being thinnest at that point.

In Fig. 'l there is shown another modified in-V sulator body indicatedgenerally by GII which is also generally similar to the insulator body'II, theinsulator body SII having formed therein a central well SI2havingan open `upper end SIS and a bottom wall H4 extending across thelower end of the well SI2. Thev bottom wall I4 ofthe insulator body IIis formed entirely of insulation material, preferably fired ceramicmaterial. The bottom wall 6I4 differs from this in that the bottom wallBI4 has one or more ne metallic wires such as platinum extendingtherethrough, these wires being inserted in the bottom wall before theilring is eiIected, the ilring serving toseal the wires in the bottomwall.

In Fig. 8 there is shown a modiiied insulator body indicated generallyby III which is again generally similar to the-insulator body I I, theinsulator body 'II I having formed therein a central well I I 2 havingan open upper end 1 I 3 and a bottomwall 1I'4 extending across the lowerend of the well 1 I2. Instead of being of insulation material as is thesolici bottom wall I4 of the insulator II, the bottomwall H4 includes aportion or is entirely made, as shown in the drawing, of conductingmaterial, such as a combination of ceramic material and a metallicpowder such as iron, nickel, chromium, or tungsten, sintered together.

The insulator bodies SII, SII, and 1II each includes a different meanswhereby a reduced potential difference is required to effect the passageof an electrical discharge or current through their respective bottomwalls M4, U4, and '|I4, as compared with the potential differencerequired to eiect the passage of a discharge through the solid bottomwall I4 oi.' insulation material of the insulator body II, where all ofthe bottom walls have the same thickness.

In Fig. 9 there is shown a spark plug indicated generally by 8I0 whichis generally similar to the spark plug I0. but in the spark plug IIB theground electrode 822 is formed by sprayed metal on thevreduced` lowerend IIS of the insulator body BI I.

It should also be noted that the'replaceable ground electrode 22 on theinsulator body II as shown preferably is screw connected with theinsulator body II. In addition to being mere- 1yy screwed on theinsulator body II, the replaceable ground electrode' 22 may be thermallysweated thereon.

- In Figs. l0, 12, and 1,3 there is shown a spark plug indicatedgenerally by SID which is generally similar to the spark plug II) withlthe exception of thel construction and arrangement of the well andcentral electrode. The spark plug 9I0 includes an insulatorb'ody 9i Ihaving formed therein'a central well SI2 having an open upper end 9I3and a bottom wall 91,4 extending across the ,lower end of the Well SI2.The well 9I2 has an increasedudiameter as compared with the diameterofuthe well I2 of the insulator body II of the spark plug III. l

the lower end of the vwell SI2 there is located a'body ofconducting'liquid preferably liquid metal SIS-I which may b e mercury ora lower melting alloy of bismuth, tin`, lead, and antimony, orsimilar'material'. There is also locatedvin the well 4SI2 ametalelectrode rod SIS, the lower end of which extends into the body ofliquid metal SIS-I, and the metal electrode rod SIE has an enlarged headSIB which is externally threaded and screwed in the internally threadedenlarged upper end SI1 of the well SI2. A body of cement 93| seals theupper portions of the electrode rod SIB between the' body of liquidmetal 9I6--I and the head sla. l l

' In the spark plug 9I0 the lower body of liquid metal SIS-I andtheelectrode rod SIS whose lower end is immersed in the body of liquidmetal QII-I constitute a composite central electrode in which the lower'end oi the body of liquid metal SIG-I always rests upon the upper faceof the well bottom wall 9 I 4. In other words the position oi' the lowerend oi the composite central -electrode of the spark plug 9I0 alwaysremains con-` stant,v where as disintegration of the lower tip of thecentral electrode rod 9 I 6 may take place if the lower Jtip of thecentral electrode rod SIG ex tends to the top surface of the well bottomwall SI4, and no body of liquid metal SIS-I is used. The'body of liquidmetal SIG-I flows into any void produced in it on top oi' the wellbottom wall 9I4.

Moreover, in the operation of an internal combustion engine, forexample, in which the spark plug SIU is in use, the hot gases in thecombustion chamber served by the spark plug SIU heats the lower :end ofthe spark plug 9I0 and the body of liquid metal` SIS-I therein causingcirculation ananas of the liquid metal SIB-I, whereby there is atransfer of heat from the lower end I3 of the insulator body SII toupper portions and surfaces of the insulator body SI I, this transfer ofheat being effected by convection of the body of circulating-liquidmetal SIS-I, as well as by its own conduction.

In Fig. ll there is shown a spark plug indicated generally by llt-I9which is generally similar to the spark plug I and includes an insulatorbody IOII having formed therein a central well I9I2 having an open upperend IIII3, and the insulator body IIII has a lower end I9I9 which hasformed therein a bore I9l2-I which has a diameter reduced from that ofthe well I9I2. An intermediate electrode shank IIN-2 is located andsealed in the bore I9I2-I and has on its upper end an enlarged headIIN-3 which fits and seals the lower end of the bore I9I2. A body ofconducting liquid IIlIB-I is located in the lower end of the well I9 I2and rests upon `the top of the enlarged head IMI-3 on the intermediateelectrode shank INS-2. A metal electrode rod IIIS is located in the wellI9I2 and has its lower end immersed in the body of conducting liquidIMS-I, and a body of cement IIII seals the upper portions of theelectrode rod VI 9I9.

In Fig. 14 there is shown a spark plug indicated generally by I IIBwhich is generally similar to the spark plug 9 I l. The spark plug I II9 includes an insulator body IIII having formed therein a central wellIII2 having an open upper end III3 and a bottom wall I I I4 extendingacross the lower end of the well III2. The insulator body IIII has areduced lower end III! having a bottom face IIII-I, and the well bottomwall IIIl is spaced above the bottom face I I II-I In the lower end III!of the insulator body IIII there is formed an internally threaded socketIII9-3 in which is screwed an externally threaded intermediate electrodeIII32. The wall IIIl may be provided. if desired, with one or moremicroscopic holes formed by puncture by an electrical discharge.

In the lower end of the well III2 there is located a body of conductingliquid IIIl-I on top of which is a layer of powdered carbon IIN- 4.There is also located in the well III2 a metal electrode rod IIIB. thelower end of which extends into the layer of powdered carbon I IIS-4.

In Fig. l there is shown a spark plug indicated generally by I2I0 whichincludes the improvements of the spark plug IIIO embodied in aconstruction which is otherwise conventional.

In Fig. 16 there is shown a spark plug indicated generally by I3I9 whichis generally similar to the spark plug I2III, with certain exceptions.The spark plug I3I0 includes an insulator body IIII with a bottom faceNIS-I and the insulator body I3I I has formed therein a well I3I2 havinga bottom wall I3II extending across the lower end of the well I3I2. Thebottom wall I3II is spaced above the bottom face I3I3-I of the insulatorbody IIII, and in the lower end I3I9 of the insulator body I3II there isformed a downwardly opening socket I3 I 9 3.

The spark plug I3I9 furthermore includes a metal ground shell |330 onthe lower end of which is a metal electrode tip |324 whose outer endextends into the socket HIS-3.

The embodiments of the present invention illustrated and describedherein are by way of example and the scope of the present invention isnot limited to the same or to the particular details thereof but iscommensurate with any and all novel subject matter contained hereinwhich may at any time properly under the patent laws be set forth in theclaims hereof or originating herein, and the elements of any such claimsare intended to include their functional or structural equivalents.

Iclaim:

1. In spark plug construction, an Insulator body having a bottom faceand the insulator body having formed therein a well with an open upperend and the insulator body including a well Vbottom wall extendingentirely across and closing the lower end of the well, the well bottomwall being spaced above the insulator body bottom face. a metal groundelectrode adjacent the lower end of the insulator'body. electrodematerial in the well, and the insulator body having formed therein adownwardly opening socket below the well bottom wall. and anintermediate electrode in the socket.

2. In spark plug construction, an insulator body having a bottom faceand the insulator body having formed therein a well with an open upperend and the insulator body including a well bottom wall extendingentirely across and closing the lower end ol.' the well. the well bottomwall being spaced above the insulator body bottom tace. a groundelectrode adjacent the lower end of the insulator body, electrodematerial in the well, and the insulator body having formed therein adownwardly opening socket below the well bottom wall. and anintermediate electrode Ain the socket.

3. In spark plug construction. an insulator body having a bottom faceand the insulator body having formed therein a well with an open upperend and the insulator body including a well bottom wall extendingentirely across and closing the lower end of the well, the well bottomwall being spaced above the insulator body bottom face, a groundelectrode adjacent the lower end of the insulator body, electrodematerial in the well, and the insulator body having formed therein adownwardly opening socket below the well bottom wall, and wnductingmaterial in thesocket.

4. In spark plug construction, an insulator body having a bottom faceand the insulator body having formed therein a well with an open upperend and the insulator body including a well bottom wall extendingentirely across and closing the lower end of the well, the well bottomwall being spaced above the insulator body bottom face, a groundelectrode adjacent the lower end of the insulator body, electrodematerial in the well, and the insulator body having formed therein aninternally threaded downwardly opening socket below the well bottomwall, and an externally threaded intermediate electrode screwed inthesocket.

HAROLD R. FEICHTER.

REFERENCES CITED The following references are of record in the file ofthis paient:

UNITED STATES PATENTS Number Name Date 1,491,752 Richey Apr. 22, 19242,072,732 Devers Mar. 2, 1937 2,093,848 Randolph et al. Sept. 2l, 19372,318,440 Wall May 4, 1943

